1. Field of the Invention
The present invention generally relates to foot-wear construction and in particular to the use of multiple shock absorption and stabilizing members incorporated into the heel portion of the midsole of the footwear.
2. Prior Art
The result of the increased popularity of exercise, as well as the necessities of everyday walking and standing, it has been recognized there is a need to alleviate and relieve the stress imposed on a person""s feet and legs. In particular, it is essential that shoes and other like footwear provide for suitable shock absorption and stability. This is particularly important where the shoes or footwear are to be used in active pursuits such as running or other athletic endeavors.
As a general rule, it is the midsole of a shoe that provides the cushioning and stability to the foot of a user. In conventional shoes used for athletic purposes, either poly-urethane foam, EVA (ethyl vinyl acetate) foam or perhaps HYTREL foam is used as the material which provides most of the cushioning of the shoe (HYTREL is a trademark of DuPont de Numerus and Co.). As stated, advanced shock absorption and stability is particularly required in athletic footwear where the user""s foot is exposed to repeated shocks from footstep impact in running and other athletic activities.
The prior art discloses a variety of footwear designs which have been developed for the purpose of improving shock absorption and stability. These prior art designs range from merely constructing the shoe sole from a softer, more resilient material to incorporating fluid-filled pads or bladders in the midsole of a shoe. In many shoe midsoles designed to increase the cushioning effects of the shoe, the increased resiliency or softness of the shoe sole provides no resistance to the tendency of the user""s foot to rotate relative to the leg upon impact, a condition generally referred to as pronation. The tendency for excessive lowering of the medial margin of the foot or excessive pronation, and a tendency for an excessive raising of the medial margin of the foot, or supination, have the potential of causing injuries to the wearer of the shoe.
One of the footwear designs disclosed by the prior art comprises a pair of tabs extending from opposite sides of the outsole of the shoe to the heel counter of the shoe for the purpose of connecting the outsole to the heel counter and increasing the lateral medial stability of the shoe. In this design, the tabs are formed as an integral part of the shoe outsole and are bonded to a heel wedge layer and midsole layer of the shoe sole as well as the heel counter. The inadequacy of this design is inherent in its construction. Since the tabs are secured to the extreme outer edges of the heel wedge and midsole, this will reduce the ability of the tabs to resist compression of the heeled wedge and midsole in the areas of the wedge and midsole inside the shoe surrounding the user""s foot.
Another design for footwear disclosed by the prior art employs one or more shock absorbers embedded within the heel portion of the midsole. The shock absorbers are typically air or fluid filled cylinders which can absorb the force of the heel and then return the energy in a controlled upward direction. Irrespective of the number of fluid filled cylinders embedded within the heel, excessive pronation of the user""s foot will occur since the air cylinders cannot properly respond to the difference in forces imposed on the medial and lateral portions of the heel.
The present invention substantially resolves those deficiencies exhibited by the designs disclosed in the prior art. The present invention employs an assembly of structural elements to achieve a result which was previously attempted by changing the material of the midsole. The elements of the present invention used to stabilize the shoe from heel strike to toe off comprise a pair of non-symmetrical, multi-lobed pods disposed between the medial and lateral portions of upper and lower shock absorbing deflectable plates mounted within the heel portion of the sole. The deflectable plates and pods are deformable upon the imposition of force and will return to their original configuration upon the removal of force. The configuration of the upper and lower plates and the non-symmetrical, multi-lobed pods improve the stabilization characteristics of the footwear and to control excessive foot pronation or supination inherent in those footwear designs disclosed by the prior art.
The present invention relates to the structure of the sole of footwear which improves shock absorption and stability. The midsole of the footwear has a heel portion and forefoot portion and an upper and lower surface. In the heel portion of the midsole, the upper surface thereof is adapted to receive the user""s heel. An upper shock absorbing deflectable plate is disposed adjacent the lower surface of the heel portion of the midsole. A central segment of the upper plate extending along the longitudinal axis thereof extends upwardly into an elongated concave surface which is disposed adjacent the bottom surface of the midsole. Upon the imposition of force on the midsole by the user""s heel, the deflectable segment will be deformed downwardly to absorb shock. When the force is removed, the deflectable segment will return to its original position.
A lower plate includes a central concave deflectable segment positioned along the longitudinal axis thereof which is adapted to be positioned adjacent the deflectable segment of the upper plate. Upon the imposition of force upon the heel of the midsole, the deformation of the deflectable segment of the upper plate will be transmitted to the deflectable segment of the lower plate. When the force is removed, the deflectable segments of both the upper and lower plates will rebound to their original orientation.
A pair of unsymmetrical stabilizing pods are disposed between the upper and lower shock absorption plates. The medial pod extends from the medial side of the sole about the rear of the shoe. The lateral stabilizing pod is spaced from the medial pod and is positioned solely along the lateral side of the shoe. Each stabilizing pod is constructed and positioned to dynamically stabilize the shoe along the direction of impact. To avoid excess pronation or supination of the shoe and the user""s foot, the hardness of the medial stabilizing pod may be greater than that of the lateral stabilizing pod.
It is an object of the present invention to provide a construction for a shoe sole which improves shock absorption and stability.
It is another object of the present invention to provide improved shock absorption and stability for a shoe through the use of cooperating shock absorbing elements.
It is still another object of the present invention to provide improved shock absorption for a shoe through the use of cooperating, deflectable plates responsive to the force of the user""s foot.
It is still yet another object of the present invention to provide improved, dynamic stability for a shoe through the use of unsymmetrical stabilizing pods.
It is still yet another object of the present invention to provide a shoe incorporating an improved shock absorption and stability system which is simple and inexpensive to fabricate.
The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objectives and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawing in which a presently preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention.